With the development of photoelectricity and semiconductor technology, flat panel display is booming. Liquid crystal display (LCD) in numerous flat displays has been applied in various aspects of production and living for its favorable characteristics such as high efficient in space utilization, low power consumption, radiationless and low disturbance of electromagnetism etc.
The drive system of the liquid crystal display generally includes a data driver, a signal controller and a common voltage generator. The signal controller provides an image data and a control signal to the data driver, wherein the control signal includes an output enable signal and a polarity reversal signal. When the falling edge of the output enable signal arrivals, the data driver outputs a positive polarity pixel voltage or a negative polarity pixel voltage relative to a common voltage generated by the common voltage generator according to the polarity reversal signal, to provide to each pixel of the liquid crystal display.
However, the common voltage generator is independent, and it is not controlled by the signal controller. Thus, when the signal controller does not output an image data and a control signal since it crashed in an abnormal state, the data driver would not output any signal, by this time, the common voltage generator still generates a common voltage (i.e., a direct voltage) normally and transmits it to each pixel, such that each pixel has been driven by the direct voltage, which results in the polarization of liquid crystal molecules after a long time, thereby the liquid crystal moleculars lose normal deflection function causing a display failure.